class Solution:
    def compress(self, chars):
        """
        :type chars: List[str]
        :rtype: int
        """
        n = len(chars)
        i , count = 0 , 1

        for j in range(1,n+1):
            if j < n and chars[j] == chars[j-1]:
                count += 1

            else:
                chars[i] = chars[j-1]
                i += 1
                if count > 1:
                    for m in str(count):
                        chars[i] = m
                        i += 1
                count = 1

        return i






        """
        Given an array of characters, compress it in-place.

        The length after compression must always be smaller than or equal to the original array.

        Every element of the array should be a character (not int) of length 1.

        After you are done modifying the input array in-place, return the new length of the array.


        Follow up:
        Could you solve it using only O(1) extra space?


        Example 1:

        Input:
        ["a","a","b","b","c","c","c"]

        Output:
        Return 6, and the first 6 characters of the input array should be: ["a","2","b","2","c","3"]

        Explanation:
        "aa" is replaced by "a2". "bb" is replaced by "b2". "ccc" is replaced by "c3".

        """
